Double 1,3-Dipolar Cycloaddition Reaction of 3-Phenylsydnone with 1,3-Dienes

Thermal reaction of 3-phenylsydnone with isoprene or 2,3-dimethylbutadiene gave 2-methyl- or 2,6-dimethyl-7-phenyl-1,7-diazatricyclo [2.2.1.02,6]heptane, together with 3-isopropenyl-1-phenylpyrazole. The former is the product of the double 1,3-dipolar cycloaddition. A similar reaction with 1,3-butadiene gave only 3-vinyl-1-phenylpyrazole.